Excitation spectrum of a two-dimensional Wigner lattice

We propose a spectroscopic method to determine the existence of an electronic Wigner lattice at a given electron density n. We derive the ‘‘perpendicular’’ excited states of the two-dimensional Wigner lattice on a dielectric layer with a metallic substrate, and compare them with the corresponding excited states of the two-dimensional electron gas at the same electron densities. The transitions from the ground to the first excited state are studied in detail and we have found a significant difference between the lattice and the gas excitation energies for n≳10^8 cm^-2. In that sense, the spectroscopy of electronic transitions can prove the existence of a Wigner lattice and a rapid change in the excitation spectrum can serve for determination of the lattice melting temperature. A linear Stark effect in the case of a Wigner lattice is also analyzed